GaAlAs Laser Research Articles

Influence of laser (660 nm) on functional recovery of the sciatic nerve in rats following crushing lesion

With the aim of accelerating the regenerative processes, the objective was to study the influence of gallium-aluminum-arsenide (GaAlAs) laser (660 nm) on functional and histomorphological recovery of the sciatic nerve in rats. The sciatic nerves of 12 Wistar rats were crushed divided into two groups: control and laser therapy. For the latter, GaAlAs laser was utilized (660 nm, 4 J/cm(2), 26.3 mW and 0.63 cm(2) beam), at three equidistant points on the lesion, for 20 days. Comparison of the sciatic functional index (SFI) showed that there was a significant difference only between the pre-lesion value of the laser therapy group and that after the 21st day in the control group. It was concluded that the parameters and methods utilized demonstrated positive results regarding the SFI over the time period evaluated.

Use of therapeutic laser for prevention and treatment of oral mucositis

Oral mucositis (OM) affects patients who are submitted to hematopoietic stem cell transplantation (HSCT) due to high doses of chemotherapy and/or radiotherapy. The purpose of this investigation was to perform a comparative study of the frequency and evolution of OM among patients subjected to therapeutic laser and to the conventional therapy (use of mouthwash called 'Mucositis Formula'). The patients were subjected to a myeloablative conditioning regimen before the allogeneic HSCT. Twenty-two patients were selected and divided into 2 groups: group I was irradiated with InGaAlP laser (660 nm) and GaAlAs laser (780 nm), 25 mW potency, 6.3J/cm(2) dose, in 10-s irradiation time, followed to conventional treatment; group II was subjected only to the conventional treatment. Both World Health Organization (WHO) scale and the Oral Mucositis Assessment Scale (OMAS) were used to evaluate the results. Data were analyzed by the non-parametric Wilcoxon test, with p<0.05 considered as statistically significant. Group I presented a lower frequency of OM (p=0.02) and lower mean scores, according to WHO and OMAS scales (p<0.01 and p=0.01, respectively). In conclusion, laser reduced the frequency and severity of OM, suggesting that therapeutic laser can be used both as a new form of prevention and treatment of OM.

Low-level Infrared Laser Therapy in Chemotherapy-induced Oral Mucositis

Oral mucositis (OM) is one of the most frequent complications of chemotherapy for which there is no standard therapy; treatment is mostly conservative. This study was conducted to determine whether low-intensity laser therapy (LLLT) can reduce the duration of chemotherapy-induced OM. A placebo-controlled randomized trial was carried out using LLLT or placebo (sham treatment). Children and adolescents with cancer receiving chemotherapy or hematopoietic stem-cell transplantation between October 2005 and May 2006 were eligible as soon as they developed OM. Patients received intervention for 5 days. The LLLT group was treated with laser GaAlAs, wavelength (lambda): 830 nm (infrared), power: 100 mW, dose: 4 J/cm, and placebo group underwent sham treatment. The grade of OM was clinically assessed by the National Cancer Institute, Common Toxicity Criteria scale. Twenty-one patients developed OM and were evaluable for analysis; 18 (86%) patients had a diagnosis of leukemia or lymphoma and 3(14%) had solid tumors. The mean age was 8.2 (+/-3.1) years. Nine patients were randomized in the laser group and 12 in the placebo-control group. Once OM was diagnosed, the patients had daily OM grading assessments before laser or sham application and thereafter until complete healing of the lesions. On day 7 after OM diagnosis, 1/9 of patients remained with lesions in laser group and 9/12 of patients in the placebo-control group (P=0.029). In the laser group, the mean of OM duration was 5.8+/-2 days and in the placebo group was 8.9+/-2.4 days (P=0.004). Our study has shown evidence that laser therapy in addition to oral care can decrease the duration of chemotherapy-induced OM. Our results confirm the promising results observed in adult cancer patients and should encourage pediatric oncologists to use laser therapy as first-line option in children with chemotherapy-induced OM.

Spin squeezing in the presence of dissipation

The transfer of spin between photons and localized atomic levels, for a chain of two-level atoms, is studied. The Hamiltonian of the system is modelled by a radiation term and by atom–atom and radiation-atom interactions. Effects due to dissipation are accounted for by atom-photon exchange-interactions of complex strength. It is found that the spin-squeezing is suppressed by dissipation. Calculations are performed for arrays of Rb atoms excited by a GaAlAs laser.

Electrophysiologic Effects of a Therapeutic Laser on Myofascial Trigger Spots of Rabbit Skeletal Muscles

To better understand the mechanisms of therapeutic lasers for treating human myofascial trigger points, we designed a blinded controlled study of the effects of a therapeutic laser on the prevalence of endplate noise (EPN) recorded from the myofascial trigger spot (MTrS) of rabbit skeletal muscle. In eight rabbits, one MTrS in each biceps femoris muscle was irradiated with a 660-nm, continuous-wave, gallium-aluminum-arsenate (GaAlAs) laser, at 9 J/cm2. The contralateral side of muscle was treated with a sham laser. Each rabbit received six treatments. The immediate and cumulative effects were assessed by the prevalence of EPN with electromyographic (EMG) recordings after the first and last treatments. Compared with pretreatment values, the percentages of EPN prevalence in the experimental side after the first and last treatments were significantly reduced (P < 0.01 for both). The change in EPN prevalence in the experimental side was significantly greater than in the control side immediately after the first and last treatments (P < 0.05). However, no significant differences were noted between the first and last treatments (P > 0.05). In our study, immediate and cumulative effects of a GaAlAs laser applied on MTrS were demonstrated on the basis of the assessment of EPN prevalence. It seems that laser irradiation may inhibit the irritability of an MTrS in rabbit skeletal muscle. This effect may be a possible mechanism for myofascial pain relief with laser therapy.

Effect of low-level laser therapy after implantation of poly-L-lactic/polyglycolic acid in the femurs of rats

This study evaluated the use of red and infrared lasers on tissue surrounding the femurs of 60 rats randomly divided into three groups after implantation of bioabsorbable plates. The control group were not subjected to laser irradiation; group A was treated with red laser [indium-gallium-aluminum-phosphide (InGaAlP) laser, wavelength 685 nm, 35 mW, continuous wave (CW), Ø = 0.06 cm, 2.23 min], and group B was subjected to infrared laser [gallium-aluminum-arsenium (GaAlAs) laser, wavelength 830 nm, 50 mw, CW, Ø = 0.06 cm, 1.41 min], both at 10 J/cm(2). Samples were stained with hematoxylin and eosin (H&E) and examined microscopically. Results showed that the laser irradiation had had a positive photobiomodulation effect on inflammation, confirmed by a better histologic pattern than that of the control group at 3 days and 7 days. Semiquantitative analysis revealed that groups A and B had a histologic score significantly greater than that of the control group at 3 days. At 21 days, histomorphometric analysis revealed a more intense inflammation in the red laser group than in the other groups. We concluded that low-level laser therapy (LLLT) has positive effects on the photobiomodulation of inflammation in the tissues surrounding the poly-L-lactic/polyglycolic acid (PLLA/PGA) bioabsorbable plate. It stimulated vascularization, fibroblast proliferation, and collagen deposition.

Combining Therapeutic Laser and Herbal Remedy for Treating Ligament Injury: An Ultrastructural Morphological Study

We examined the ultrastructural morphology (number of collagen fibrils, mean and mass-averaged diameter) of isolated and combined treatments of a therapeutic laser and herbs for medial collateral ligament (MCL) injury in rats. Twenty-eight rats, divided into seven groups: laser (L), herb (H), laser + herb (LH), laser control (LC), herb control (HC), laser sham (LS) and herb sham (HS), were studied. Right MCL of groups L, H, LH, LC and HC were transected, while that of LS and HS remained intact. Group L received 9 treatment sessions of GaAlAs laser with a dosage of 3.5 Jcm(-2); group H received herbal plaster treatment; groups LH had combined treatments of laser and herb; group LC had placebo laser; group LS had no treatment; groups HC and HS received only bandage without herb. All MCLs were analyzed using transmission electron microscopy at 3 weeks. Differences (p < 0.05) existed in mean fibril diameters among groups. Core mass-averaged diameters of groups L and H were larger than the control groups (LC and HC). Fibril diameter of group LH (combined treatment) was even larger and approaching that of the intact MCL. Combined therapeutic laser and herbal treatment hastened collagen fibril maturation in MCL repair.

Pockels effect in yttrium aluminum borate single crystals

Experimental measurements of linear electro-optical coefficients are reported for YAl3(BO3)4 (YAB) single crystals for the two principal tensor components xyz and yyy at the wavelength of a CW semiconducting GaAlAs laser emitting at 1040 nm. We have found the values of the Pockels coefficients to be equal to 0.21 ± 0.06 and 0.56 ± 0.08 pm/V for 123 and 222 Pockels components, respectively. Additional measurements performed for the thin-cut samples with the thickness varying within the 100–500 μm have confirmed the values of the corresponding parameters. We have eliminated a contribution of the piezooptical coefficients as well as for other disturbing factors. We have established that the crystals with a different number of defects do not show any differences, which indicate the principal role of the borate clusters on the observed effects. The temperature changes are very low (due to a low ionic contribution), and do not exceed 5–6%, which indicates the low contribution of the electron-phonon to the Pockels effect. Because the YAB crystals possess a very large photothermal damage (more than 15 GW/cm2) and are only slightly temperature dependent. Hence, they may be proposed as promising materials for high-power laser electro-optic modulators.

Morphometric and histological analysis of low-power laser influence on bone morphogenetic protein in bone defects repair

Bone morphogenetic proteins (BMPs) are secreted signaling molecules belonging to the transforming growth factor-beta (TGF-beta) superfamily. The objective of this study was to determine how gallium-aluminum-arsenium (GaAlAs) 650 nm laser influenced the action of BMPs on bone defects created in rat femurs. The sample consisted of 24 male albino Wistar rats. Group 1 was composed of rats with bone defects filled with bone-inducing substance, with the application of low-power laser. Group 2 contained rats with bone defects filled with a bone-inducing substance, without the application of low-power laser. Group 3 rats had bone defects not filled with a bone-inducing substance, with the application of low-power laser. Group 4 rats had bone defects and no treatment (control group). A bone defect was produced with drills. In groups 1 and 2 the defects were filled with a bone-inducing substance. The animals were treated with GaAlAs (50 mW) laser, energy density 4 J/cm(2), for 80 ss on a 1 cm(2) area. Groups 2 and 4 were used as control. Bone samples were removed for histological procedures and morphometric analysis on the 7th, 14th and 21st days after surgery. Results obtained were subjected to statistical analysis. Rejection level for the null hypothesis was 0.05. Statistical differences were found in the comparison between group 1 (G1), G2, G3 and G4 [analysis of variance (ANOVA); P < 0.0134]. There was a statistically significant correlation between groups 1 and 4 (P < 0.01). The results of other correlations by Tukey's post-hoc test were: group 1 vs group 3 (P = 0.341), group 1 vs group 2 (P = 0.862), group 2 vs group 4 (P = 0.061), group 2 vs group 3 (P = 0.744), and group 3 vs group 4 (P = 0.249). We concluded that the association of low-power laser with a bone-inducing substance produced better results than when low-power laser or BMPs were used alone.

Effect of 670-nm Laser Therapy and Dexamethasone on Tissue Repair: A Histological and Ultrastructural Study

In this study we investigated the role of extracellular matrix elements and cells during the wound healing phases following the use of low-level laser therapy (LLLT) and anti-inflammatory drugs. There are few scientific studies that characterize the possible interactions of LLLT and anti-inflammatory medications. Thirty-two rats submitted to a wound inflicted with a 6-mm-diameter punch. The animals were divided into four groups: sham treated, those treated with the GaAlAs laser (4 J/cm(2), 9 mW, lambda = 670 nm, spot size 28.27 x 10(2) cm(2)), those treated with dexamethasone (2 mg/kg), and those treated with both LLLT and dexamethasone. After 3 and 5 d, the cutaneous wounds were assessed by histopathology using polarized light and ultrastructural assessment using transmission electron microscopy. Changes seen in polymorphonuclear inflammatory cells, edema, mononuclear cells, and collagen fiber deposition were semi-quantitatively evaluated. The laser-treated group demonstrated increased collagen content and better arrangement of the extracellular matrix (p < 0.05). Fibroblasts in these tissues were increased in number and were more synthetically active. In the dexamethasone group, the collagen was shown to be non-homogenous and disorganized, with a scarcity of fibroblasts. In the group treated with both types of therapy, fibroblasts were more common and they exhibited vigorous rough endoplasmic reticulum, but they had less collagen production compared to those seen in the laser group. LLLT alone accelerates post-surgical tissue repair and reduces edema and the polymorphonuclear infiltrate even in the presence of dexamethasone.

Evaluation of the Effect of the GaAlAs Laser on Subgingival Scaling and Root Planing

To evaluate the auxiliary effect of the low-intensity laser in subgingival scaling and root planing by analysis of its clinical aspects, as well as its analgesic potential during the procedure. Despite the large number of studies conducted on low-intensity laser energy, few clinical studies are available on periodontics. Ten patients were selected and submitted to measurement of six sites per tooth, four teeth per hemiarch (960 sites in all). All patients then received subgingival scaling and root planing. Besides periodontal treatment, the test side was also submitted to laser application. The analysis comprised measurement of probing depth, clinical attachment level, and gingival index. Laser energy was applied at a wavelength of 780 nm (35 J/cm(2), 70 mW, 20 sec per site) for preoperative analgesia, and scaling and root planing were performed with application of laser energy at a wavelength of 780 nm (35 J/cm(2), 70 mW, 20 sec) for analgesia, and at a wavelength of 630 nm (8.8 J/cm(2), 35 mW, 10 sec) for healing. The patients filled out a visual analogue scale to assess the pain they felt during the procedure. After 24 and 48 h, the laser was again applied at the wavelength of 630 nm, and the patients were re-evaluated after 3 d. There was a reduction in gingival inflammation, yet without a statistically significant difference between the study and control sides, both in clinical aspects and evaluation of pain during the procedure. Utilization of the diode laser as an auxiliary in subgingival scaling and root planing did not provide any apparent clinical benefit for teeth with shallow to moderate pockets.

Effect of low-power gallium-aluminum-arsenium laser therapy (830 nm) in combination with bisphosphonate treatment on osteopenic bone structure: an experimental animal study

Laser therapy is able to modulate cell metabolism and accelerate the repair of fracture. Little attention has been given to the effect of laser on bone with osteopenia or osteoporosis. The purpose of our study was to verify the effect of laser therapy in combination with bisphosphonate on osteopenic bone structure. The 35 Wistar female rats used were divided into five groups: (1) sham-operation rats (control), (2) ovariectomized (OVX'd) rats with osteopenia, (3) OVX'd rats with osteopenia treated with laser, (4) OVX'd rats with osteopenia treated with bisphosphonate and (5) OVX'd rats with osteopenia treated with bisphosphonate and laser. Groups 3 and 5 were given daily 6 mg doses of bisphosphonate orally. Groups 4 and 5 underwent low level laser therapy [gallium-aluminum-arsenium (GaAlAs) laser, 830 nm, 50 mW and 4 J/cm(2)] on the femoral neck and vertebral segments (T13-L2). Both treatments were performed over an 8-week period. Rats from the osteopenic control and osteopenic + laser groups presented marked osteopenia. In the osteopenic + bisphosphonate group, the trabecular bone volume in vertebra L2 was significantly greater than in the osteopenic control group. Notably, in the association between laser and bisphosphonate, the trabecular bone volume was significantly greater in vertebrae L2 and T13 and was similar to that in the sham-operation control group. It was concluded that the laser therapy associated with bisphosphonate treatment was the best method for reversing vertebral osteopenia caused by the ovariectomy.

Effect of soft laser and bioactive glass on bone regeneration in the treatment of bone defects (an experimental study)

This study aimed to investigate the influence of low-power gallium-aluminium-arsenide (GaAlAs) laser [830 nm, continuous wave (CW), 40 mW and fluence 4 J/cm(2)] on the healing of surgically created bone defects in rats treated with bioactive glass graft material. Surgical bone defects were created in the mandibles of 36 Wistar rats divided into two groups, each consisting of 18 rats. Group I was treated with bioactive glass plus laser irradiation. Group II was treated with graft material only. The animals were killed at 4 weeks, 8 weeks and 12 weeks postoperatively for histological examination. Laser irradiation had significantly accelerated bone healing at 4 weeks and 8 weeks in comparison with that at the sites not irradiated. However at 12 weeks, complete healing of the defects had occurred with no difference detected. Our results have confirmed the positive effect of soft laser in accelerating bone regeneration.

Effect of soft laser and bioactive glass on bone regeneration in the treatment of infra-bony defects (a clinical study)

This study aimed to investigate the influence of low-power 830 nm gallium-aluminium-arsenide (GaAlAs) laser [continuous wave (CW) 40 mW and fluence 4 J/cm(2), with total energy density of 16 J/cm(2)] on the healing of human infra-bony defects treated with bioactive glass graft material. Twenty patients with chronic periodontitis and bilateral infra-bony defects were included. Using a split mouth design, we treated 20 defects with bioactive glass plus laser irradiation during surgical procedures and on days 3, 5, 7 postoperatively; 20 contra-lateral defects were treated with bioactive glass only. Clinical probing pocket depths, clinical attachment levels and standardized periapical radiographs were recorded at baseline and at 3 months and 6 months postoperatively. At 3 months there was a statistically significant difference between the laser and non-laser sites in the parameters investigated. However, at 6 months, no difference was observed. Our results have confirmed the positive effect of soft laser in accelerating periodontal wound healing.

Efeito da terapia com laser de arsenieto de gálio e alumínio (660Nm) sobre a recuperação do nervo ciático de ratos após lesão por neurotmese seguida de anastomose epineural: análise funcional

CONTEXT: Peripheral nerve injuries result in sensory and motor losses in the innervated area and can hinder individuals’ daily activities. Objective: The objective was to analyze the influence of applying gallium-aluminum-arsenide (GaAlAs) laser (660Nm) on the functional recovery of the sciatic nerve in rats. METHODS: The sciatic nerve of 12 Wistar rats was subjected to injury consisting of neurotmesis and epineural anastomosis. The rats were divided into two groups: control and laser therapy. After the injury, a GaAlAs laser was used (660Nm, 4J/cm², 26.3mW and 0.63cm² beam) at three equidistant points on the injury, for 20 days. Footprint impressions were obtained from the animals before and seven, 14 and 21 days after the surgical procedure and the sciatic functional index (SFI) was calculated. RESULTS: Comparison of the SFI did not show any significant difference (p>0.05) between the two groups. CONCLUSIONS: The parameters and methods used for the laser therapy did not produce any effect on the SFI over the period evaluated.

Comparative study in desensitizing efficacy using the GaAlAs laser and dentin bonding agent

Objective To compare the clinical efficacy of the GaAlAs laser and dentin bonding agent in treating dentin hypersensitivity. Methods One hundred and forty teeth from 70 patients diagnosed with dentin hypersensitivity, were divided into two groups: In group I, teeth were irradiated with 30 mW GaAlAs laser for 1 min and in group II, teeth were applied with dentin bonding agent. Sensitivity was assessed by tactile and thermal tests, measured with the criteria proposed by Uchida at baseline and after treatment; immediately, at 15 and at 30 days. Results The reduction of dentin hypersensitivity was observed in both treatments using the GaAlAs laser and dentin bonding agent. However, a greater reduction was observed over time up to day 15 and no significant change was observed between days 15 and 30. Statistically significant differences in the level of dentin hypersensitivity between bonding agent and the GaAlAs laser were found at each observation period ( p < 0.05). Conclusion The GaAlAs laser had less desensitizing efficacy compared with dentin bonding agent. However, the desensitizing effect of the GaAlAs laser still could be considered an effective therapy for treating dentin hypersensitivity.

Radiation dynamics of injection lasers with saturating absorber in resonator

The structure of a GaAlAs laser with saturating absorber in a resonator and a method of research of the light generation dynamics with the use of an optical stroboscopic oscilloscope OSO-1 which has a time resolution of ~30 ps are described. The dependence of the succession frequency of radiation peaks on the parameters of pumping current impulses and the direct bias current in injection heterolasers with saturating absorber in a resonator is determined.

Failure of low-level laser therapy to boost healing of venous leg ulcers in surgically and conservatively treated patients

Summary Objective: To evaluate in a randomized open-label clinical trial the ability of adjuvant low-level laser therapy (LLLT) to improve healing of venous leg ulcers in surgically and conservatively treated patients. Patients and methods: Eighty three patients with venous leg ulcers were included in this study. Patients in groups 1 and 2 were treated surgically while patients in groups 3 and 4 were treated conservatively. Patients in groups 1 and 3 were additionally treated with the LLLT (GaAlAs laser, 810 nm, 4 J/cm2, 65 mW) once daily, 6 times a week for 7 weeks. Results: After therapy comparison of completely healed wounds, statistically significant differences were seen between groups 1 and 3 (p=0.02), 1 and 4 (p= 0.02), 2 and 3 (p= 0.02), 2 and 4 (p=0.02) in favor of groups 1 and 2. Comparison of the relative change of wound total surface area indicated statistically significant differences between groups 1 and 3 (p=0.002), 1 and 4 (p=0.002), 2 and 3 (p=0.002), 2 and 4 (p=0.002) in favor of groups 1 and 2. Comparison of the other parameters also demonstrated a more efficient therapy effects in groups 1 and 2 than in group 3 and 4. There were no statistical differences in all examined parameters between groups 1 and 2 (p&gt;0.05), 3 and 4 (p&gt;0.05). Conclusion: The application of the LLLT does not enhance healing of venous leg ulcers in surgically and conservatively treated patients. A well conducted surgical operation is much more efficient than conservative pharmacological procedures.

THE EFFECT OF GaAlAs DIODE LASER ON PRE-SPORTS WARMING UP AND POST-SPORTS COOLING DOWN

Low reactive level laser therapy (LLLT) involving low incident levels of laser light, is known for its normalizing effect on abnormalities of living bodies. A joint study by Keio University Institute of Physical Education Japan Medical Laser Laboratory and the Ohshiro Clinic was conducted to investigate the application of the GaAlAs diode laser in the field of sports medicine during pre-training or pre-competition warm up and post-training cooling down. The ‘Sit and Reach’ test, blood oxygenation and pulse rates were measured in 17 athletes, 15 males and 2 females, before laser irradiation (A), after the first laser irradiation (B), after physical exertion (C) and after a second laser irradiation (D). The Oh-Lase HT 2001 semi-conductor laser was applied to the neck while the subject adopted a sitting position on the floor with the legs stretched forward. The subjects were requested to stretch (toe-touch) as far as possible followed by another 8 seconds of laser irradiation while the subjects were stretched and were measured for maximum stretching distance. The procedure was repeated. When statistical significance was evaluated there were significant changes between A and B, A and C, A and D, B and D, and C and D in the performance of the Sit and Reach Test, whereas significant differences in heart rate were seen between A and C, B and C, B and D, and C and D, and significant differences between A and B, A and D, B and C, and C and D in the blood oxygen saturation level. The results where significant differences between A and B, and C and D imply that the use of the GaAlAs laser during warm up and cool down is beneficial.

Cultured epithelial cells response to phototherapy with low intensity laser

Little is known about the intracellular response of epithelial cells to phototherapy. The aim of this in vitro study was to analyze the effect of phototherapy with low-energy lasers with different wavelengths and powers on cultured epithelial cell growth under different nutritional conditions. Epithelial cell cultures (Vero cell line) grown in nutritional deficit in culture medium supplemented with 2% fetal bovine serum (FBS) were irradiated with low-energy laser from one to three times with a GaAlAs laser (660 nm) and InGaAlP (780 nm), 40 and 70 mW, respectively, with 3 or 5 J/cm2. Cell growth was indirectly assessed by measuring the cell mitochondrial activity. Nonirradiated cell cultures grown in nutritional regular medium supplemented with 10% FBS produced higher cell growth than all cultures grown in nutritional deficit irradiated or not. The overall cell growth of cultures grown under nutritionally deficit conditions was significantly improved especially when irradiated with 780 nm for three times. Phototherapy with the laser parameters tested increases epithelial cell growth rate for cells stressed by growth under nutritionally deficient states. This cell growth improvement is directly proportional to the number of irradiations; however, was not enough to reach the full cell growth potential rate of Vero epithelial cell line observed when growing under nutritional regular condition.